Not by much, (if at all) and this can be a good thing. It does not make you impotent or sterile. (If it did — there would be no Rastafarians left!)
Give those testicles a rest, already! Marijuana is certainly _not_ birth control, please don’t let your lover tell you it is.
Many people think that marijuana enhances their sex lives. It is not an aphrodisiac, that is, it does not make people want to have sex. What it does do for some people is make everything more sensual — it makes food taste better and feelings and emotions more vivid.